REFIT OF PHOTOTHEODOLITE 19/1318 AND ITS
APPLICATION TO CLOSE RANGE PHOTOGRAMMERTY
Wang Li,Fan Qiulin,Liao Hongbin
Associate Professor
Institute of Seismology of State Seismological Bureau
Commission V
ABSTRACT: The refitting method of the phototheodolite 19/1318 is briefly introduced. The change of
lens distortion effect after refitting of camera is discussed. The application of the refitted
19/1318 to close range photogrammetry and some results are suggested.
KEY WORDS: Phototheodolite 19/1318, Refit.
1 INTRODUCTION
The close range photogrammetry has been applied
extensively day by day with the advancement of
science and production. The various instruments
for close range photography are put forward inter-
nationally. However,it is difficult that the new
instruments are imported largely in a great
country like China which belonges in the
developping country. A lot of phototheodolite
19/1318 are produced and imported in China in the
past. Statistically, there are nearly a hundred or
more sets in the productive and scientific
departments of China. Could the 19/1318 be used
for close range photogrammetry? We have done the
test and obtained certain results since 1980.
2 BRIEF INTRODUCTION OF REFIT
OF PHOTOTHEODOLITE 19/1318
2.1 Estimation of Increment of Principal Distance
Being of service to the topometry, the principal
distance of phototheodolite 19/1318 is fixed and
focused at infinity. The hyperfocal distance H is
computed from the equation:
H=f2/ek (1)
Where :, the tolerant diameter of the circle of
confusion, letting ¢=0.1mm; k, the relative
aperture of camera, k-25 for 19/1318; f, the focal
distance of camera, f-200mm. We obtain H-16m.
The image distance d is not equal to principal
distance f because the object distance becomes
short in close range photography. In order to keep
the imagery condition, the principal distance of
camera must be increased.
Using the af to indicate the increment from image
to prime focal place, the following equation can
be written from the geometric optics:
1/f = 1/D + 1/(£ + af)
then
Af =f2/(D-f) (2)
where D, the distinct camera-to-subject distance.
The foreground distance D1-H-D/(H*D) and the back-
ground distance D2=H-D/(H-D) can be evaluated with
H and D. Then the depth of field is
AD = D2-D1 (3)
The relational values among D, Af and AD are
calculated as in table 1.
Table 1 Relational Values Among D, Af and AD
No. Af (mm) D (m) AD (m)
À 4.8 8.0 5.3 — 16.0
B 9.8 4.0 3.2 —: 5.3
C 16.3 2.5 2.92 — 3.1
2.2 Application of washer
The principal distance of taf
camera is increased by |o O Es
using a washer to insert °
between the camera magazi-
ne and the lens place
(Fig.1). The thickness of
washer is computed from
equation 2. Three washers
(A,B,c) with thicknesses
listed in table 1 are
processed. Applying these
washers individually and »
combinatively, the photo- |O O =)
theodolite 19/1318 can LT
relize different close
range photographies above
one meter.
Fig.1 Washer
3 DETERMINATION OF LENS DISTORTION OF
PHOTOTHEODOLITE 19/1318 AFTER REFIT
The lens of 19/1318 is projected so that the dis-
tortion in focusing at infinity is less than 6pm.
Generally, the effect of lens distortion is
changed with the change of photographic distance.
Thus it is necessary to study the change of
distortion effect of 19/1318 after refitting.
The lens distortion cosists of the radial and the
tangential one. Ordinarily, the first effect is
main. Therefore, the change of main terms in
distortion effect of 19/1318 after increment of
principal distance is determined according to the
collinearity equation:
ai (X-Xs)+b1 (Y-Ys)+c1(Z-Zs)
X-X, +ax=f
a2(X-Xs) *b2(Y-Ys) *c2(Z-Zs)
(4)
a3 (X-Xs) *b3(Y-Ys) *c3(Z-Zs)
Z-Z,t4z-f
a2(X-Xs) *b2(Y-Ys) *c2(Z-Zs)
in which
AXzk1l(x-x,)r?-*k2(x-x,)r^-*(z-z.) (1*ds) Sindf
(5)
AZzki(z-z,)r?-*k2(z-z,)r^-* (z-z, ) [(1*ds) CosdP-1]
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